Electric motor control with malfunction detection

Abstract

A motor for an electromobile includes a rotor having permanent magnets and a stator coil for generating an output torque when fed with a motor current. A rotor position detector or resolver is connected to the spindle of the rotor for detecting the magnetic position of the rotor in terms of a voltage waveform and a motor controller controls the output current to the motor on the basis of the magnetic position signal coming from the rotor position detector. A first malfunction detecting circuit detects any malfunction of the rotor position detector in response to an abnormal voltage waveform coming from the rotor position detector. A second disconnection detecting circuit detects a disconnection of the motor controller from the invertor which develops drive current for the motor. A control unit outputs a signal to the motor controller for stopping the motor in response to a signal from either the first malfunction detecting circuit or the second disconnection detecting circuit.

What is claimed is: 
     
       1. An electric motor having a control with malfunction detection comprising: a motor including a rotor having permanent magnets and a stator coil energizable by a multiphase current for generating an output torque when fed with a motor current;   rotor position detecting means connected to the spindle of said rotor for detecting the magnetic position of said rotor and for generating a voltage waveform characterizing the detected magnetic position;   a motor controller for controlling the multiphase current to said motor stator coil on the basis of the magnetic position waveform from said rotor position detecting means;   a comparator circuit for comparing the magnetic position waveform with a predetermined voltage and for outputting a pulse signal in accordance with the comparison;   a pulse observing circuit for observing the pulse signal from said comparitor circuit and for outputting a malfunction signal if said pulse signal contains no pulse in a constant period; and   a control unit for outputting a signal to said motor controller for stopping said multiphase current to said motor stator coil in response to the malfunction signal from said pulse observing circuit.   
     
     
       2. An electric motor having a control with malfunction detection according to claim 1, wherein said rotor position detecting means generates two voltage waveforms which characterize the detected magnetic position;   said comparator circuit receives the two waveforms from said rotor position detecting means, compares each of the waveforms with the predetermined voltage and outputs two pulse signals in accordance with the respective comparisons; and   said pulse observing circuit outputs a malfunction signal if either of the two pulse signals outputted from said comparator circuit contains no pulse in a constant period.   
     
     
       3. A motor control circuit for an electric motor including a motor rotor having a motor spindle with permanent magnets, and a motor stator coil energizable by a multiphase motor current for generating a output torque on the motor spindle, the control circuit comprising: rotor position detecting means including (a) an exciting circuit for outputting a predetermined exciting AC voltage, and (b) a resolver having a resolver rotor connected to the motor spindle and a resolver stator wherein said resolver rotor and said resolver stator include a primary winding for receiving the exciting AC voltage and a pair of secondary windings for outputting respective AC voltage waveforms indicating the rotative position of said resolver rotor which in turn indicates a magnetic position of said motor rotor;   a magnetic detector for detecting the AC voltage waveforms from the secondary windings and outputting a magnetic position signal;   a motor controller for controlling the multiphase motor current to said motor stator coil on the basis of the magnetic position signal from said magnetic detector;   a comparator circuit for comparing the AC voltage waveforms from the secondary windings with a predetermined voltage and for outputting respective pulse signals in accordance with the comparison;   a pulse observing circuit for observing the pulse signals from said comparitor circuit and for outputting a resolver disconnection detection signal if at least one of said pulse signals contain no pulse in a constant period; and   a control unit for outputting a signal to said motor controller for stopping said multiphase current to said motor stator coil in response to the resolver disconnection detection signal from said pulse observing circuit.